1. Field of the Invention
This invention relates to electrically initiated expendable payload dispenser systems and, in particular, to an ejector dispenser system having multiple payload cartridges the firing of which is controllable over two connecting wires.
2. Description of the Prior Art
In both military and non-military environments, when it is desired to distribute certain types of ejectable payloads over a wide area, it is common practice to mount the payloads within a dispenser system carried aloft by an aircraft and to eject those payloads over a predetermined area. Typically, in a military context the payload may take the form of military ordinance, smoke generators, photoflash flares, radar detection jammers, propaganda leaflets or the like. Non-military payloads may include fertilizer, seed or advertising materials.
The dispenser system--whether to be used for a civilian or for a military purpose---typically contains a dispenser assembly comprising a dispenser block and an associated control module. The dispenser block is a member which is provided with any predetermined number M of receptacles, or holes, which are designed to receive one expendable payload unit therein. The control module is physically and electrically coupled to the dispenser block and contains the necessary electronic circuitry and connections to control the ejection of the payloads in each payload unit. The dispenser assembly is mounted in any convenient location on the aircraft, with suitable connections being provided between the control module and the aircraft's electrical system. In addition, the control module is electrically connected to firing controls disposed in a location accessable to the pilot of the craft.
A typical chaff dispenser carries thirty expendable payload units or cartridges, although dispensers having fewer and more than this number are also common. Each of such units is typically a square in cross section and about eight inches long although other configurations exist. Each payload unit may be likened to a shotgun shell having an expendable payload which is ejected and having a case or liner which typically remains in the dispenser after the payload is ejected, although some systems operate with an ejectable liner.
The dispensing mechanisms vary, but the most common type includes a pyrotechnic ejection system. Such a system uses an applied electrical signal to heat a bridge wire in a pyrotechnic gas generator referred to as a "squib" or sometimes as an "impulse cartridge". The heated, resistive bridge wire ignites the propellant charge in the ejection squib and the resultant gas pressure ejects the payload from the cartridge or unit. Thus, the system operates much like an electrically initiated shotgun shell.
The squib case holds all of the parts of the dispensing or ejection system and serves as electrical ground connection. The closure disc retains the propellant in the main chamber of the squib until the propellant is ignited, at which time the closure disc is ruptured by the gas pressure generated by the burning propellant. An electrical contact post, insulated from the squib case by a glass or plastic insulator, provides "hot wire" connection to an applied triggering current. The bridge wire is welded to the electrical contact post and to the squib case. Other squib configurations also exist.
When a proper electrical signal is applied between the electrical contact post and the squib case, the bridge wire is heated up and ignites the propellant. The buring propellant generates gas pressure which ruptures the closure disc allowing the gas to pressurize the volume underneath the piston in the payload liner. The piston transmits a pushing force to the payload and, therethrough, to the end cap. The end cap is forced out of the payload liner and then the payload is forced out of the payload liner (i.e., ejected) by the moving piston. The piston is also ejected.
The dispenser carrying the multiple cartridges is electrically connected so that each cartridge receives its signal, in turn, from an electrical contact of a "sequencer" switch, typically a rotary switch or equivalent, which moves from one position to the next.
Solid state switches may also be used in place of the rotary sequencer switch to initiate the desired cartridges.
Existing dispenser systems fall into one of two categories. The first category are those systems wherein a single expendable payload is put into each hole of the system. The second category are those dispenser systems that put multiple expendable payloads into each hole of the dispenser.
For the single expendable payload-per-hole dispenser systems, a common ground is normally employed for the cartridges, which is most often the chassis of the aircraft, or other vehicle. The connections to the sequencer switch include one hot wire running from a separate contact on the sequencer to each hole of the dispenser, thereby providing means for sequentially and separately electrically triggering the squibs. The sequencer, as noted above, functionally operates either as a rotary switch with a movable contact that moves through the individual cartridge connections, or in the solid state sequencer switch, as a firing current source using solid state devices to connect the individual cartridges to the voltage source, providing firing currents, one at a time, to each individual squib. The firing current heats the bridge wire to ignite the ejection charge, which causes ejection of the payload. Thus, one pair of electrical contacts is all that is required for each cartridge in such a system.
In the case of prior art dispenser systems using multiple expendable payloads per hole (cartridge), the wiring is more complex. For simplicity, assume only two payloads in each dispenser hole. In such case, a common ground may be employed; however, two "hot" electrical connections have heretofore been connected to each cartridge, one to the squib operating in conjunction with each payload. Therefore, two hot electrical connections or "firing" pins are required to each dispenser hole to make contact with the ignitors of the dual payloads. Hence, such a system is a three-wire system with three contacts for each hole (two hot connections and one ground connection). Such a system could also use one hot electrical connection and switch the ground between the squibs in the sequencer switch, but three wires would still be required to each hole.
Other variations in the prior art have included as many as four payloads stacked end-to-end or side-by-side in each hole. As can be seen, this has required at least five electrical contacts (four hot contacts and one common ground) for each hole.
As technology has advanced, it has become possible to achieve the desired expendable payload characteristics with smaller expendables. For example, if two expendables could be installed in the place of one, system effectiveness would be vastly increased since more expendables could be carried in the same dispenser volume. In order to minimize modification of existing dispensing systems, it is preferable to avoid physically modifying the dispenser units and aircraft wiring and to instead modify the dispenser electronics (e.g., the sequencer electronics) and/or the expendable unit electronics (i.e., the squib-related electronics) to allow two-wire operation for separately igniting the multiple pay-loads in a single cartridge.
Therefore, it is a feature of the present invention to provide an improved multiple payload cartridge input connection for separate ignition of the payloads therein using only two wires for connection thereto.
It is another feature of the present invention to provide an improved multiple payload cartridge having means for insuring against the simultaneous ignition of the squibs therein by a single applied electrical pulse, and having means for igniting squibs individually upon command.